String Handling (Cambridge (CIE) O Level Computer Science)

Revision Note

Author

Robert Hampton

Expertise

Computer Science Content Creator

String Handling

What is string manipulation?

String manipulation is the use of programming techniques to modify, analyse or extract information from a string
Examples of string manipulation include:
- Case conversion (modify)
- Length (analyse)
- Substrings (extract)

Case conversion

The ability to change a string from one case to another, for example, lower case to upper case

Function	Pseudocode	Python	Output
Uppercase	`Name ← "Sarah"` `OUTPUT UCASE(Name)`	`Name = "Sarah"` `print(Name.upper())`	"SARAH"
Lowercase	`Name ← "SARAH"` `OUTPUT LCASE(Name)`	`Name = "SARAH"` `print(Name.lower())`	"sarah"

Function

Pseudocode

Python

Output

Uppercase

Name ← "Sarah"

OUTPUT UCASE(Name)

Name = "Sarah"

print(Name.upper())

"SARAH"

Lowercase

Name ← "SARAH"

OUTPUT LCASE(Name)

Name = "SARAH"

print(Name.lower())

"sarah"

Length

The ability to count the number of characters in a string, for example, checking a password meets the minimum requirement of 8 characters

Pseudocode	Python	Output
`Password ← "letmein"` `OUTPUT LENGTH(Password)`	`Password = "letmein"` `print(len(Password))`	7
`Password ← "letmein"` `IF LENGTH(Password) >= 8` `THEN` `OUTPUT "Password accepted"` `ELSE` `OUTPUT "Password too short"` `ENDIF`	`Password = "letmein"` `if len(Password) >= 8:` `print("Password accepted")` `else:` `print("Password too short")`	"Password too short"

Pseudocode

Python

Output

Password ← "letmein"

OUTPUT LENGTH(Password)

Password = "letmein"

print(len(Password))

Password ← "letmein"

IF LENGTH(Password) >= 8

THEN

OUTPUT "Password accepted"

ELSE

OUTPUT "Password too short"

ENDIF

Password = "letmein"

if len(Password) >= 8:

print("Password accepted")

else:

print("Password too short")

"Password too short"

Substring

The ability to extract a sequence of characters from a larger string in order to be used by another function in the program, for example, data validation or combining it with other strings
Extracting substrings is performed using 'slicing', using specific start and end to slice out the desired characters
Substring has a start position of 1 in pseudocode and 0 in Python

Pseudocode	Python	Output
`Word ← "Revision"` `OUTPUT SUBSTRING(Word, 1, 3)`	`Word = "Revision"` `print(Word[0:2])`	"Rev"
`Word ← "Revision"` `OUTPUT SUBSTRING(Word, 3, 6)`	`Word = "Revision"` `print(Word[2:5])`	"visi"

Pseudocode

Python

Output

Word ← "Revision"

OUTPUT SUBSTRING(Word, 1, 3)

Word = "Revision"

print(Word[0:2])

"Rev"

Word ← "Revision"

OUTPUT SUBSTRING(Word, 3, 6)

Word = "Revision"

print(Word[2:5])

"visi"

Worked Example

The function Length(x) finds the length of a string x. The function substring(x,y,z) finds a substring of x starting at position y and z characters long. The first character in x is in position 1.

Write pseudocode statements to:

Store the string “Save my exams” in x
Find the length of the string and output it
Extract the word exams from the string and output it

[6]

Answer

X ← "Save my exams"

[1] for storing string in X

OUTPUT LENGTH(X)

[1] for calling the function length. [1] for using the correct parameter X

Y ← 9

Z ← 5

OUTPUT SUBSTRING(X,Y,Z)

[1] for using the substring function.

[1] for correct parameters

[1] for outputting length and substring return values

You've read 0 of your 0 free revision notes

Get unlimited access

to absolutely everything:

Downloadable PDFs
Unlimited Revision Notes
Topic Questions
Past Papers
Model Answers
Videos (Maths and Science)

Join the 100,000+ Students that ❤️ Save My Exams

the (exam) results speak for themselves:

Next topic

Did this page help you?

String Handling (Cambridge (CIE) O Level Computer Science)

Revision Note

String Handling

What is string manipulation?

Case conversion

Length

Substring

Worked Example

You've read 0 of your 0 free revision notes

Get unlimited access

Join the 100,000+ Students that ❤️ Save My Exams

Author: Robert Hampton